The Role of Auxin Metabolism in Root Meristem Regeneration by <i>Pinus lambertiana</i> Embryo Cuttings

Abstract

Abstract Since the existence of root promoting substances that consist of a complex between auxin and another molecule has been suggested, we have examined the role of auxin conversion products in root regeneration by Pinus lambertiana embryo cuttings. Auxin conversion products were detected using radioactive forms of the auxins IAA (indoIe‐3‐acetic acid), NAA (a‐napthaleneacetic acid) and 2,4‐D (2,4‐dichlorophenoxyacetic acid). 10 −7 M NAA was more effective than 10 −6 M IAA at promoting rooting, yet it formed conversion products much less rapidly. Also continuous exposure to IAA was necessary for optimum root formation. Based on these and other findings, we conclude that free auxin, and not the conversion products we detected, is essential to root meristem formation.